The present invention relates generally to apparatus and methods for treating septal defects, and more particularly to apparatus and methods for closing a patent foramen ovale or other septal defect.
During development of a fetus in utero, blood is generally oxygenated by the mother""s placenta, not the fetus"" developing lungs. Most of the fetus"" circulation is shunted away from the lungs through specialized vessels or foramens that are open during fetal life, but generally close shortly after birth. Occasionally, however, these foramen fail to close and create hemodynamic problems, which may ultimately prove fatal unless treated.
One defect that may occur is a patent foramen ovale (xe2x80x9cPFOxe2x80x9d), which may occur between the left and right atria of the heart. During fetal life, an opening called the foramen ovale allows blood to pass directly from the right atrium to the left atrium (bypassing the lungs). Thus, oxygenated blood from the placenta may travel through the vena cava into the right atrium, through the foramen ovale into the left atrium, and from there into the left ventricle for delivery via the aorta to the fetus"" body. After birth, with pulmonary circulation established, the increased left atrial blood flow and pressure causes the functional closure of the foramen ovale. This closure is then followed by the anatomical closure of the foramen ovale.
In some humans, however, the foramen ovale fails to completely close. This condition can pose serious health risks for the individual, particularly if the individual has other heart abnormalities. For example, recent studies suggest an association between the presence of a patent foramen ovale and the risk of paradoxical embolism or stroke. See P. Lechat J et al., Prevalence of Patent Foramen ovate in Patients with Stroke, N. Engl. J. Med. 1988;318: 1148-1152.
Still other septal defects may occur within a septum between the various chambers of the heart, such as atrial-septal defects (ASDs), ventricular-septal defects (VSDs), and the like. To close such defects, open heart surgery may be performed to ligate and close the defect. Such procedures are obviously highly invasive and pose substantial morbidity and mortality risks.
Alternatively, catheter-based procedures have been suggested. These may involve introducing umbrella or disk-like structures into the heart that include opposing expandable structures connected by a hub or waist. Generally, the device is inserted through the defect, and the expandable structures are deployed on either side of the septum to secure the tissue surrounding the defect between the umbrella or disk-like structure in an attempt to seal and close the defect. Such devices, however, involve frame structures that often support membranes, either of which may fail during the life of the patient being treated, opening the defect and/or releasing segments of the structure within the patient""s heart.
Accordingly, apparatus and methods for closing septal defects, and in particular a patent foramen ovale, would be considered useful.
The present invention is directed to apparatus and methods for closing septal defects, including, but not limited to, a patent foramen ovale.
In a first aspect of the invention, an apparatus for closing a septal defect includes a clip formed from a elastic material having at least two penetrating tines and an opposing retaining end. The clip is biased so as to project the at least two penetrating tines distal to the opposing retaining end, wherein when the bias is removed, the at least two penetrating tines move laterally apart from one another.
In accordance with another aspect of the present invention, a delivery apparatus for delivering a clip, such as that described above, is provided that includes an outer catheter and a pusher member that are slidably coupled to one another. The catheter may be a tubular member including proximal and distal ends and a lumen therebetween, the distal end having a size for insertion into a blood vessel or other body lumen. The clip may be carried within the lumen of the outer catheter, preferably, with the tines disposed distally to the retaining end.
The pusher member may be an inner catheter or other elongate member that is disposed within the lumen of the outer catheter. The pusher member may include a distal end that may be disposed proximate the retaining end of the clip, the pusher member being movable axially relative to the tubular member for ejecting the clip distally from the lumen.
An actuator may be provided on the proximal end of the tubular member and/or the pusher member for advancing the pusher member relative to the tubular member. Preferably, the actuator may limit advancement of the pusher member.
In a further alternative, the delivery apparatus may include an imaging device including an imaging element associated with the distal end of the tubular member for imaging near or beyond the distal end of the tubular member. For example, the imaging device may be an angioscope or ultrasound device that may be received within a lumen of the tubular member or may be a separate device that may introduced independently into the patient but used in conjunction with the delivery apparatus during a procedure.
In another alternative, the clip has a single tine and an opposing retaining end. The clip is biased so as to project the single tine distal to the opposing retaining end. When the bias is removed, the clip transforms into a geometric shape such as a xe2x80x9cVxe2x80x9d, xe2x80x9cUxe2x80x9d, xe2x80x9cSxe2x80x9d, or xe2x80x9cLxe2x80x9d. The opposing retaining end may have an optional head to prevent the clip from completely passing through the septum wall of a heart.
In accordance with yet another aspect of the present invention, a method is provided for closing a patent foramen ovale or other septal defect within a patient""s heart. Generally, the septal defect includes one or more flaps of tissue partially detached from a septum wall between first and second chambers of the heart, the flap(s) of tissue and surrounding tissue of the septum wall defining a septal opening through the septum wall.
A clip, such as that described above, is advanced, in a stressed state, through the patient""s vasculature until the clip is disposed adjacent to the septal opening. The tines of the clip penetrate the flap of tissue and pass into the second chamber of the heart. After the clip has penetrated the flap of tissue (i.e., septal defect), the clip transitions to its relaxed state so as to at least partially close the septal opening.
It is an object of the invention to provide a clip apparatus for the closure of septal defects, such as a patent foramen ovale. It is a further object of the invention to provide a delivery device for the delivery of the clip apparatus to the defect area. It is yet a further object of the invention to provide a method of closing a patent foramen ovale using the clip apparatus. Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.